1. Field of the Invention
This invention relates to the production of paper or paperboard and more particularly to a process for improving the retention and/or drainage properties of paper or paperboard stocks during sheet formation.
2. Brief Description of the Prior Art
Pulps which are used for papermaking fall into the two main categories of chemical and mechanical with intervening categories which can be referred to as semichemical and chemimechanical. In the chemical pulps lignin is dissolved out of the wood structure to a greater or lesser degree with the result that the wood fibres may be separated without recourse to any substantial mechanical processing. An example of a chemical pulping process is the Kraft process in which the chips of wood are digested with a strongly basic solution of sodium sulphide. In semichemical pulping processes chemical digestion is less severe and some degree of mechanical processing is necessary to achieve separation of the fibres. In chemimechanical pulping processes the chemical digestion part of the process is still less severe. A marked characteristic of chemical pulps is that the cellulosic fibres largely escape fragmentation and are relatively long.